The present invention relates to a speaker diaphragm and more particularly relates to improvement in acoustic characteristics of a diamond type diaphragm used for speakers.
Typical diamond type speaker diaphragms are disclosed in Japanese Patent Publication Sho. 55-33237 and Japanese Patent Laid-Open Sho. 59-143498.
The diamond type speaker diaphragm of the Publication Sho. 55-33237 is produced by ion beam vacuum evaporation of carbon ion and made up of a carbon material close in crystal construction and physical properties to diamond. The diamond type speaker diaphragm of the Laid-Open Sho. 59-143498 is produced by a CVD (chemical Vapour Deposition) process and made up of a diamond type carbon material.
These diamond type speaker diaphragms on one hand exhibit excellent acoustic characteristics in the middle and treble frequency ranges, i.e. in the region up to several times ten kHz thanks to their large Young's moduli. On the other hand, however, they are very low in efficiency in acoustic conversion (electrocoustic transduction) due to their large specific gravities and accompanied with resonance in the treble range due to their small internal loss. As a result, these conventional speaker diaphragms generate tones with unpleasant tone colours resulting in harsh sounding audio.